Gaseous electric discharge lamp device



Aug. 13, 1940. N. w. H. ADDINK 2,211,599

GASEOUS ELECTRIC DISCHARGE LAMP DEVICE Filed May 25, 1938 I 5 HI! INVENTOR ATTRNEY Patented Aug. 13, 1940 UNITED STATES PATENT OFFICE Nicolaas W. H. Addink, Eindhoven, Netherlands,

assignor to General Electric Company, a corporation of New York Application May 25, 1938, Serial No. 210,055 In Germany June 5, 1937 5 Claims.

The present invention relates to gaseous electric discharge lamp devices generally.

The light emitted by gaseous electric discharge lamp devices has a line spectrum as compared to the band spectrum of the light emitted by incandescent lamps; Luminescent materials which emit visible light when irradiated by light from gaseous electric discharge lamp devices are useful in conjunction with such devices to increase the efliciency thereof and to improve the color of the light emitted thereby. Preferably such a material is used in the form of a coating surrounding or partly surrounding the discharge path in the discharge device which coating, in the case of devices operating with very high container temperatures, is applied to an envelope enclosing the discharge device or to one or more screens mounted in the space between the en-'. velope and the lamp container. Zinc sulphide and zinc cadmium sulphide have been found useful for such purposes heretofore.

The object of the present invention is to improve the efiiciency of and the color of the light emitted by gaseous electric discharge lamp devices of the above type. Still further objects and advantages attaching to the device and to its use and operation will be apparent to those skilled in the art from the following particular description.

The zinc sulphide and zinc-cadmium sulphide preparations now sold commercially as luminescent materials for use in conjunction with gaseous electric discharge lamp devices are of the wurtzite rather than the sphalerite form. The crystal form of these modifications are different, as is well known, the sphalerite form crystallizing in the isometric system and the wurtzite form crystallizing in the hexagonal system. Various methods of preparing these materials and descriptions of the materials are given at pages 591 to 594, volume VII of the Dictionary of Applied Chemistry, Thorpe, published 1925 by Longmans, Green and Co. of New York and London. I have discovered that the light output of these sulphides when these materials are mounted in light receiving relation to the luminous discharge of .a gaseous electric discharge lamp device is increased and the color of the light emitted by the device is improved when the sulphide is of the sphalerite form rather than the wurtzite form. I have discovered further that the increase in the light output of these luminescent sulphides of the sphalerite form over the light output of such materials of the wurtzite form is dependent upon the temperature of these materials during the operation of the discharge; that the increase in the light output is appreciable at temperatures as high as 160 C. and that the difference in light output increases as the temperature of the luminescent material decreases. For example, I have demonstrated that at a temperature of 140 C. the light output of the sphalerite form of zinc sulphide and zinc cadmium sulphide is 14% greater than the light output of the wurtzite form of these materials. I have demonstrated, further, that at 120 C. the light output of the sphalerite form of these materials is about greater than the light output of the wurtzite form. Further, the sphalerite form of these materials emits a broader spectral l5 band than the wurtzite form thereof so that the spectrum of the light emitted by a lamp device comprising such materials of the sphalerite form approaches more closely the spectrum of an incandescent lamp.

In the drawing accompanying and forming part of this specification one type of electric lamp device embodying the invention is shown in a front elevational, partly sectional view.

Referring to the drawing the lamp device com- 25 prises a gaseous electric discharge device having an elongated tubular container i, such as a quartz container, having an inside diameter of about 6.5 mm. and an outside diameter of about 10 mm. Thermionic activated electrodes 2 and 3p 3 are mounted at opposite ends of said container l and are heated to and maintained at an electron emitting, arc discharge supporting temperature by the discharge incident thereat. Said electrodes are separated a distance of about 22 mm. Said container i has a starting gas therein, such as argon, at a pressure of about 20 mm.

A quantity of mercury is contained in the container l and is present in such amount that the discharge lamp device is capable of operation at w elevated vapor pressures, such as a vapor pressure of 10 atmospheres and higher, and operates with a constricted arc discharge of high intrinsic brilliancy.

The discharge lamp device is mounted in a sealed envelope 1 and is supported therein by current leads t and 5 connected to the electrodes zand 3, respectively, and fused into the press 6 of the stem of the envelope I. Said current leads 4 and 5 are connected to the contacts on the base 8 attached to the envelope 5 in the usual manner. The envelope 1 is evacuated, or is filled with an inert gas, such as nitrogen, when desired. Preferably the current input is about watts and under operating conditions the part of con- 5 tainer I between the electrodes 2 and 3 is at a temperature higher than 600 C.

The inner surface of the envelope 1 has a lumlnescent coating 9 thereon consisting of zinc sulphide of the sphalerite form. The coating 9 is applied to the inner surface of said envelope 1 by methods now known in the art, such as by using a volatilizable binding material. The luminescent coating 9 is excited by radiation from the discharge lamp device and emits light of a longer wave length than that by which it is excited to complement and supplement the visible light emitted by the discharge lamp device. As disclosed above it is critical to the success of the present invention that the temperature of the coating 9 during the operation of the device be lower than 160 C. and preferably lower than 140 C. When the diameter of the spherical part of the envelope I is about 10 cm. and the current input of the discharge lamp device is about watts the coating 9 is at a temperature lower than C.

The lamp device described above is a highly efiicient one and the spectrum of the light emitted thereby is useful for illuminating purposes generally.

It is not essential that the'coating 9 consist entirely of the sphalerite form of zinc sulphide or zinc-cadmium sulphide since good results can be obtained when the coating contains the sphalerite form of such material in major proportion and the wurtzite form of these materials in minor proportion.

The luminescent coating of the present invention is useful in conjunction with other types of discharge lamp devices provided the gaseous atmosphcre in such lamps emits rays capable of exciting the luminescent material to light emission and the luminescent coating is mounted in such position relative to the discharge that such rays impinge thereon and that the temperature thereof is Within the limits set forth above. One device of this type is a mercury vapor discharge lamp device which operates with an unsaturated vapor atmosphere at about atmospheric pressure and which has a container pervious to the exciting rays, which container is enclosed by a sealed envelope. Preferably the coating 9 is applied to the inner surface of the envelope of such a device. Another device of this type is a low pressure mercury vapor discharge lamp device having an elongated, positive column discharge and provided either with cold electrodes or thermionic electrodes. Preferably the coating 9 is applied either to the inner or outer surface of the container of such devices.

While I have shown and described and have pointed out in the annexed claims certain novel features of the invention, it will be understood that various omissions, substitutions and changes in the forms and details of the device illustrated and in its use and operation may be made by those skilled in the art without departing from the broad spirit and scope of the invention, for example, other luminescent materials may be mixed with the sulphides to improve the color of the light emitted by the lamp, when desired.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. An electric lamp comprising in combination a coating of material comprising a luminescent sulphide of the sphalerite form and a gaseous electric discharge lamp device which emits rays capable of exciting said material to light emission, said coating being mounted in such position relative to the discharge in said discharge device that the exciting rays impinge thereon and the temperature of said material during the operation of said device is lower than C.

2. An electric lamp comprising in combination a coating of material comprising a luminescent zinc sulphide of the sphalerite form and a gaseous electric discharge lamp device which emits rays capable of exciting said material to light emission, said coating being mounted in such position relative to the discharge in said discharge device that the exciting rays impinge thereon and the temperature of said material during the operation of said device is lower than 160 C.

3. An electric lamp comprising in combination a coating of material comprising a luminescent zinc-cadmium sulphide of the sphalerite form and a gaseous electric discharge lamp device which emits rays capable of exciting said material to light emission, said coating being mounted in such position relative to the discharge in said discharge device that the exciting rays impinge thereon and the temperature of said material during the operation of said device is lower than 160 C.

4. An electric lamp comprising a gaseous electric discharge lamp device, a sealed envelope enclosing said lamp and a luminescent coating capable of light emission under irradiation by said lamp device, said coating being mounted on the inner surface of said envelope and containing a luminescent sulphide of the sphalerite form, the distance between said coating and said lamp device being such that the temperature of said coating is lower than 160 C. during the operation of said lamp device.

5. A gaseous electric discharge lamp device of the positive column type having an elongated, tubular container, a gaseous atmosphere therein, electrodes sealed therein and a coating of luminescent material on said container, said coating containing a luminescent sulphide of the sphalerite form, the temperature of said container being less than 160 C. during the operation of. said device.

NICOLAAS W. H. ADDINK. 

